Electronic consumer circuits, in particular those used is areas at risk of fire and/or explosions, are typically protected by means of voltage limiters from excessive elevations of initially applied voltages, or in other words overvoltages that would increase beyond the voltage level permitted for a given circuit.
Circuit configurations that have at least one semiconductor element, connected in a shunt to the input voltage of a downstream consumer circuit and having a variable ohmic resistor, are often used as voltage limiters.
For instance, in U.S. Pat. Nos. 4,589,049 and 4,849,845, circuit configurations for monitoring and/or regulating, in particular limiting, a supply voltage for a downstream consumer circuit are described that include the following:                a voltage monitoring electronics unit, reacting the supply voltage, for generating a control signal that signals whether the supply voltage is lower than an associated tolerance value;        a shunt electronics unit, triggered by the control signal, with at least one semiconductor element for regulating and guiding a shunt current driven by the supply voltage,                    and the supply voltage drops at least in part via the shunt electronics unit, and            the shunt current flows through the shunt electronics unit at least whenever the control signal signals that the supply voltage is greater than the tolerance value.                        
When such circuit configurations, serving as active voltage limiters, are used for electronic consumer circuits that are used in areas at risk of fire and/or explosion, particular in circuits that are intended to meet European standards EN 50019 and/or EN 50020, at least the voltage-limiting shunts are made redundant, for instance by means of multiple cascading, in terms of current-carrying capacity and/or voltage strength, because of the required enhanced or intrinsic safety.
This in turn necessarily means increased expense for components and/or wiring, and typically this also means an increased demand for space for such voltage limiters.